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paulgipe
Posts: 299
Joined: Sat Aug 02, 2014 4:23 pm
Delivery Date: 20 Oct 2014
Leaf Number: 311200
Location: Bakersfield, CA 93305
Contact: Website

Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Sat Aug 31, 2019 8:42 am

We are approaching the two-year anniversary of leasing a 2017 Chevy Bolt EV. This is a good time to take stock of any degradation in the Bolt's traction battery capacity and how that compares with a 2015 Nissan Leaf we leased previously.

Everyone who uses a smartphone understands that lithium-ion batteries degrade over time and with use. The question is how much over what period of time.

The traction battery is at the heart of an electric vehicle (EV). It's what makes it go. Battery degradation is important because it can affect the EVs utility. Significant degradation can reduce an EVs range sufficiently to affect how the car is used. It can also affect the car's resale value.

Nissan was the first manufacturer to offer a mass-market EV. A few years after introducing the Leaf, Nissan began fielding complaints about rapid battery degradation in hot climates, such as Phoenix, Arizona. Subsequently, Nissan was forced to offer warranty battery replacements. They also began changing battery chemistry as a result. Our 2015 Leaf used what the online community called the "lizard battery" because it was presumably more resistant to high temperatures.

On the other hand, minor battery degradation is expected and may never affect how the EV is actually driven. A good example is the reported performance of Tesla's Model S. Though there's measured degradation, it's considered minor even in high-mileage vehicles that are several years old. (See Tesla battery degradation at less than 10% after over 160,000 miles, according to latest data for details on one vehicle and Tales from a Tesla Model S with 450,000 miles: Battery life, durability, and more on another.)

Chevy introduced the Bolt in late 2016. Since its introduction, at east one driver, Eric Way of News Coulumb fame, has driven the Bolt more than 70,000 miles and reported his findings. He concluded that the degradation wasn't significant: ~8%. It certainly hasn't affected how he drives his Bolt. He drives it hard--often charging it to 100% and then depleting it to only a few percent state-of-charge on his weekend forays. (See Way's video report at Chevy Bolt EV: 70,000 Mile Battery Degradation.)

Traction Battery Capacity & Range

The 2015 Nissan Leaf had a nominal 24 kWh traction battery. However, not all that capacity was used to drive the car. Some 22 kWh were usable, giving the car an official EPA range of 84 miles when the car was new. So though the car had a nominal 24 kWh traction battery, in practice drivers never saw that.

When we first began driving the Leaf, the car often estimated we had a range in excess of 90 miles and occasionally in excess of 100 miles on a full charge.

Unlike the Leaf, our Chevy Bolt's nominal traction battery capacity of 60 kWh is what was available to drive our car, giving it an official EPA range of 238 miles on a full charge.

There's some debate among the online community over whether the usable capacity of the traction battery is really 60 kWh. However, when we've run the state-of-charge down to around 10% of remaining capacity, the range indicator suggests we may have started with 60 kWh or a little bit more.

Early in our operation of the Bolt we drove it 238 miles around town here in Bakersfield. We consumed 55.3 kWh at an efficiency of 4.3 mi/kWh and had a SOC of 10% remaining. The range indicator said we had 27 miles left. In another case we drove it 232 miles, consuming 52.6 kWh at an efficiency of 4.4 mi/kWh with 14% SOC remaining. The range indicator said we had 36 miles left. (See Driving the Chevy Bolt EV--Our Impressions.)

The Bolt's estimate of the range available on a full charge hasn't changed much in the two years we've driven the car. Typically the mid-value of the Bolt's three range estimates has hovered around 250 miles of range on a full charge.

Charging & Driving History

We intentionally drove the both the Leaf and the Bolt in the manner we'd drive any car. We took no special precautions. We used the EVs as we'd expect most consumers would use them.

In the first year of operation of both vehicles, we often charged to 100% and just drove the cars until we needed to charge again. In the case of the Bolt, after the first year we began using "Hill-top Reserve" to charge the car up to 88% of its full capacity, but we weren't religious about it.

While Bakersfield may not be as hot as Phoenix, Arizona, it is hot here in the summer--blistering hot. It's not uncommon here for temperatures to exceed 105 F (40 C) for several days in July, August, and September. It's not unusual for temperatures here to exceed 113 F (45 C). Any EV that can survive several Bakersfield summers probably will not be susceptible to temperature degradation.

Leaf Spy & Torque Pro

There's no universally accepted way for consumers to measure an EV's traction battery capacity. In general, manufacturers prefer that consumers remain in the dark. As long as the car does what it was advertised to do, consumers needn't worry about their battery pack, or so their thinking may go.

Fortunately, pioneering EV drivers are technically savvy and some have hacked the communications from the cars' computers through the OBD (On-board Diagnostic) port.

For Nissan's Leaf, there's a commercial app, Leaf Spy, which interprets the signals from the OBD port with a compatible OBD reader. (See Leaf Spy--an Essential Tool for Serious Nissan Leaf Drivers.) One of the parameters measured by Leaf Spy is kWh of battery capacity.

It's not as simple for Bolt drivers, but hackers have determined how to configure Torque Pro to interpret the signals from an OBD reader. (I use the same OBD reader in the Bolt as I did in the Leaf. See Peeking Inside the Bolt's Brain Reveals Valuable Secrets.)

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Capacity Loss

We measured from a little less than 2 kWh loss of capacity in our 2015 Nissan Leaf to as much as 2.5 kWh over 8,500 miles of use in the 22 months that we monitored the EV's health. The loss of capacity ranged from 8.6% to as much as 11.5% before we returned the car to Nissan at the end of the lease. (See Battery Degradation Two-Year Status Report: 2015 Nissan Leaf.)

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Despite the Leaf's loss of capacity, it didn't affect how we used the car. It did reduce my comfort level on the steep climbs out of Bakersfield, but we didn't change how we drove the car.

We've since downsized to only one car and that's the Chevy Bolt. We're driving it much more than we ever drove the Leaf. Nevertheless, the traction battery has degraded half that of the Leaf over considerably more miles driven. Over 13,000 miles in 12 months, the battery has degraded 3.6% from a measured high of 61.1 kWh. From the nominal capacity of 60 kWh, the battery pack has degraded less than 2% over the nearly 20,000 miles we've driven the car.

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Other anecdotal data points can be tracked down on the various EV forums. For example, one forum participant bought a used Bolt with 100,000 miles and a loss of only 5.5% from the nominal 60 kWh for the Bolt as measured by Torque Pro. If this is the norm, it puts the longevity of the Bolt's traction battery on a par with that from Tesla. (The entire thread can be read at Battery Degradation after 100,000 miles?)

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Estimated Range

The estimated range of our Leaf gradually declined during the three years we leased the vehicle. The range decreased about 10 miles. At 4 miles/kWh that's a decline of about 2 kWh, which is in line with the measured capacity loss.

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We haven't seen any discernible decline in the estimated range of the Bolt. We still see the high estimate of range exceeding 300 miles, depending on how the Bolt was driven before we charged the car. On one recent 180-mile round trip to the mountains where we averaged 4.9 miles/kWh, the Bolt's high range estimate reached 353 miles--the best we've seen since we leased the car nearly two years ago.

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In short, the battery degradation we've measured in the Bolt is minimal and hasn't had any effect on our range or how we use the car.
Bakersfield, California
2017 Bolt LT with DCFC, leased 11/09/17
2015 Nissan S with QC, leased, returned
2013 Chevy Volt Premium, used 10/3/16, sold
L2; ClipperCreek HCS-40; Jesla; JDapter Stub
http://www.wind-works.org

gbrance
Posts: 21
Joined: Thu Dec 31, 2015 8:21 am
Delivery Date: 31 Dec 2015

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Thu Sep 05, 2019 9:29 am

Thank for the excellent summary of the battery degradation you have seen between a Bolt and a Leaf.

My wife's family lives in Bakersfield so I am very familiar with how hot "Bako" can get!!

DougWantsALeaf
Posts: 911
Joined: Fri May 10, 2013 8:21 pm
Delivery Date: 18 May 2013
Leaf Number: 407811
Location: Chicago North Side

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Thu Sep 05, 2019 11:58 am

It would certainly be great if the manufacturers had to submit degradation data for comparison purposes. I think that would be a great thing for the EPA to publish for the benefits of consumers.

Not to be the pessimist, but if you draw a line of regression off of your low range points (for all 3 bands) on the GOM, what does that suggest the rate of decline is for your bolt?

I don't have the great detailed data from my 2013 Leaf, but from my foggy memory, in winter, my GOM in year 0 was a low 87 miles and in year 6 it was a low of 71, or just about 20% total degradation. (Car was garaged, so winter charge up was at mid 40's in the depth of winter). We lost a bar after completing 5 years, and still had 11 bars after completing 6, so that seems about in line.

From your graph, it looks like you went from 200 miles to 175 miles at the bottom of the spikes, or 12%.

Now the real question. Have you done 353 miles on a charge?
2019 SV Plus Silver
2013 Leaf SV
100 Mile Club Member (Number 87)
Max distance on 13 Leaf: 120 miles
Max distance on 19 Leaf: 242 Highway 4.5 miles/kWh (4.9 KWh remaining)

Evoforce
Posts: 916
Joined: Wed Mar 04, 2015 9:58 pm
Delivery Date: 28 Feb 2015
Location: Fountain Hills Arizona

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Thu Sep 05, 2019 4:04 pm

Nice summary!
*2011 Leaf 1 bought 2/28/15 @ 28,000ish mi 10 bar (8 bars @ 11/25/15 @ 37,453 ) (New lizard @ 39,275 mi @ 1/20/2016) Now 52,166 mi.
*Tesla Model S 61,000 mi
*2011 Leaf 2 bought 4/28/15 @ 24,000ish mi 12 bar (new lizard Dec. 2014 @ 22,273 mi) Now 35,485 mi

User avatar
paulgipe
Posts: 299
Joined: Sat Aug 02, 2014 4:23 pm
Delivery Date: 20 Oct 2014
Leaf Number: 311200
Location: Bakersfield, CA 93305
Contact: Website

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Fri Sep 06, 2019 7:34 am

DougWantsALeaf wrote:
Thu Sep 05, 2019 11:58 am

Now the real question. Have you done 353 miles on a charge?
Doug,

No, but as I report I've done 200+ miles with a remaining reserve that brings it up to about 4 kWh/mi for 60 kWh. We typically drive 2-3 hours before we have have a bathroom break or take a walk. We charge then if we can. ;)

Paul
Bakersfield, California
2017 Bolt LT with DCFC, leased 11/09/17
2015 Nissan S with QC, leased, returned
2013 Chevy Volt Premium, used 10/3/16, sold
L2; ClipperCreek HCS-40; Jesla; JDapter Stub
http://www.wind-works.org

DougWantsALeaf
Posts: 911
Joined: Fri May 10, 2013 8:21 pm
Delivery Date: 18 May 2013
Leaf Number: 407811
Location: Chicago North Side

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Fri Sep 06, 2019 7:57 am

Yep, that sounds consistent with other Bolt owners I know. (some have told me they have achieved 275 miles (not sure if all highway or not), but haven't heard more then that).

I would have gone for the bolt over a leaf if the cargo (with seats up) was a bit bigger and my wife liked the layout (she thought it looked to much like a space ship). The car drives a bit different than the Leaf, which also wasn't to my wife's liking.
2019 SV Plus Silver
2013 Leaf SV
100 Mile Club Member (Number 87)
Max distance on 13 Leaf: 120 miles
Max distance on 19 Leaf: 242 Highway 4.5 miles/kWh (4.9 KWh remaining)

DaveinOlyWA
Posts: 14101
Joined: Sat Apr 24, 2010 7:43 pm
Delivery Date: 16 Feb 2018
Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Fri Sep 06, 2019 9:56 am

Nice report but really quite predictable. The LEAFs smaller pack means more cycling (which isn't all that bad) and more time at higher SOC (which is bad) than a larger pack. So the ratio of degradation pretty much matches the ratio of pack sizes.

The problem as I see it is the new Bolt has much more custom charging settings (ala Tesla) while the LEAF with its 250 mile range... is still spitting sand out of its mouth and wondering why its not enjoying it...
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

alozzy
Posts: 1369
Joined: Fri Jan 20, 2017 4:25 pm
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Location: Vancouver, BC
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Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Fri Sep 06, 2019 10:24 am

The jury is still out on whether lower depths of discharge on a larger pack completely explains the high degradation rate of 24 kWh packs. I'm still betting that active TMS reduces the degradation rate and that the 40 kWh and 62 kWh LEAF packs will suffer higher degradation rates vs EVs with similar sized packs that use a TMS.

We should have an answer to that in a couple more years...
Vancouver, CA owner of a 2013 Ocean Blue SV + QC, purchased 01/2017 in WA
Zencar 12/20/24/30A L1/L2 portable EVSE
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Loving my first BEV :D

DaveinOlyWA
Posts: 14101
Joined: Sat Apr 24, 2010 7:43 pm
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Leaf Number: 314199
Location: Olympia, WA
Contact: Website

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Fri Sep 06, 2019 11:00 am

alozzy wrote:
Fri Sep 06, 2019 10:24 am
The jury is still out on whether lower depths of discharge on a larger pack completely explains the high degradation rate of 24 kWh packs. I'm still betting that active TMS reduces the degradation rate and that the 40 kWh and 62 kWh LEAF packs will suffer higher degradation rates vs EVs with similar sized packs that use a TMS.

We should have an answer to that in a couple more years...
That jury will never find its way back to the courtroom. Smaller packs by design, have to spend more time at a higher SOC mostly due to excessive range anxiety. So you have an 80 mile car and a 250 mile car. You drive 25 miles in each. Both have PLENTY of charge to do it again but which WILL be plugged in daily? TBH; both should have an SOC maintained no higher than 60% but that is not how we roll.

On the flip side, we have a TON of evidence of people running to very low SOCs daily, multiple charging events mostly DC, etc. and have far far far exceeded the curve.

We have a 2015 LEAF here and ya ya, its the Pacific Northwest the ultimate in Li longevity (which isn't all that true) but does it explain him at well over 130,000 miles and not even 'halfway' to losing his FIRST bar?

The reality is a car driven that much doesn't have time to sit at a high SOC for any significant amount of time. So its not the cycling we want to look at. Its the time at high SOC that is the killer. Its the lack of custom charge levels in the LEAF that is criminal. Tell the jury to go home. Case dropped from lack of evidence.
2011 SL; 44,598 miles. 2013 S; 44,840 miles.2016 S30 deceased. 29,413 miles. 2018 S40; 15,000 miles, 478 GIDs, 37.0 kwh 109.81 Ahr , SOH 94.61, Hx 120.15
My Blog; http://daveinolywa.blogspot.com" onclick="window.open(this.href);return false;

amissionleaf
Posts: 18
Joined: Mon Oct 08, 2018 1:53 pm
Delivery Date: 23 Mar 2017
Leaf Number: 302367

Re: Battery Degradation Comparison Chevy Bolt EV and Nissan Leaf

Wed Oct 02, 2019 10:20 am

Now Leaf also has 62 kwh pack, so it might be more fair to compare leaf e+, bolt and model 3 std-plus. but this comparison results won't be available until years. only we have that results and if leaf e+ shows significant more degradation level than the others we can conclude active cooling system is a must.
2014 S; 33500 miles, returned with 12 bars.
2017 SV; 20000+ miles, sw update 10/8/18, feels like 15 miles range back,.
date miles SOH
10/19/2018 20853 91.5%
09/28/2019 26745 85.98%

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